1. Field of the Invention
The present invention relates, generally, to a manual-mode operating system for a robot.
2. Description of the Related Art
Generally, in an application wherein an end-effector is attached to a robot for working, it is practiced to adjust the orientation of the end-effector, in a manual mode, to teach a task that the end-effector should execute on an object (e.g., a workpiece) or for the optional changing of the orientation of the end-effector. For example, in a robot for handling, such as transferring, a workpiece (so called a handling robot), when teaching a manipulator, with a hand attached thereto, the task of picking up a workpiece placed on a workpiece support by the hand or the task of placing the workpiece gripped by the hand onto the workpiece support, it becomes necessary to change the orientation of the hand in various ways.
In the case where a manual mode operation is carried out, it is generally required that a coordinate system for describing the manual mode operation (referred to as “a manual-mode coordinate system” in this application) is designated to a robot controller, except for the case where a certain control axis provided in a manipulator is designated to have the manipulator carry out an act in association with the designated control axis. As for the orientation adjustment of the end-effector, the existing tool coordinate system, in which the tip end point of a tool (one of the end-effectors) is the origin, is often used as the manual-mode coordinate system to be designated, but there are also cases where a newly provided manual-mode coordinate system is designated. In order to set a new manual-mode coordinate system, techniques such the three-point teaching or the six-point teaching are used.
The manual-mode coordinate system in relation to the orientation adjustment of the end-effector is normally set on or near the end-effector, and, in the manual mode operation, the direction of rotation in a coordinate of the set manual-mode coordinate system is designated so as to change the orientation of the end-effector about the origin of the manual-mode coordinate system (or the tool end point in the case of the tool coordinate system) in the designated direction of rotation. In this connection, the manual-mode coordinate system is generally a rectangular three-axis coordinate system, and it is possible to perform the orientation change about the origin under a rotating motion about each coordinate axis of the manual-mode coordinate system by, for example, selecting either one of six keys (+X axis rotation, −X axis rotation, +Y axis rotation, −Y axis rotation, +Z axis rotation, −Z axis rotation) of a teaching unit provided for the robot and operating it for an input operation.
However, in the conventional procedure, if it is attempted to set the origin of the manual-mode coordinate system at a position desired as a center of the orientation adjustment of the end-effector, a setting condition cannot be visually confirmed, so that the manual mode operation should be repeated in a trial-and-error manner to select a most suitable coordinate system. This is somewhat complicated work requiring an operator's skill. Furthermore, even when the manual-mode coordinate system has been set successfully at a proper position, it is necessary to reset the manual-mode coordinate system if the working environment changes.
In view of this, another procedure may be adopted, in which the origins of a plurality of manual-mode coordinate systems are previously set at a plurality of positions on or near the end-effector and the most effective origin and the most effective manual-mode coordinate system are selectively used in correspondence to the change in the working environment of the robot to adjust the orientation of the end-effector in the manual mode. However, in this procedure, it is, in practice, difficult to set a large number of the origins of coordinates to correspond to all possible changes in the working environment, and also it becomes necessary to use many working steps to set the plural origins of coordinates, which is liable to increase the operator's load. These problems in the orientation adjusting motion for the end-effector are associated not only with the hand but also with various end-effectors other than the hand.
Similar problems may also arise in the case where, for a robot in an off-line programming system (so-called a simulation robot) rather than an actual robot, the orientation adjustment of the end-effector is carried out in a virtual three-dimensional simulation space as previously provided. In other words, when the orientation of the end-effector of the simulation robot is adjusted in a manual mode in the simulation space, no countermeasure has been taken to easily and properly set the manual-mode coordinate system, so that it has conventionally been difficult to efficiently implement proper off-line teaching by freely adjusting the orientation of the end-effector of the simulation robot.